The present invention relates to a feeding apparatus for material sheets, capable of delivering material sheets stored in layers in a hopper one after another.
A continuous blank feeder described in Jpn. Pat. Appln. KOKAI Publication No. 3-620 issued in Japan can be given as an example of a background art related to a feeding apparatus of this type. This conventional continuous feeder comprises a hopper that stores blanks stacked in layers and a suction head that can attract each blank and draw it out through the outlet of the hopper. The suction head can continuously deliver the blanks as it reciprocates. If the hopper outlet faces downward, for example, the opposite side edges of the stack of the blanks are supported at the hopper outlet. In this state, the lowest blank in the hopper is kept as flat as possible by means of its elastic force and detained in the hopper without dropping from the hopper outlet. As the suction head reciprocates between the hopper outlet and conveyor rollers, it first gets into the hopper and attracts the lowest blank. Then, the suction head retreats from the hopper outlet, thereby delivering the attracted blank from the hopper. The delivered blank is released from suction by the suction head and delivered onto the conveyor rollers. It is transported to a packaging machine on the conveyor rollers. Thus, the suction head can continuously perform the operation for delivering the blanks from the hopper by simply repeating the reciprocating operation. Usually, the speed of this delivery operation is set according to the production capacity of the packaging machine. If the packaging cycle is speeded up, therefore, the blank delivery speed is also increased.
In a delivery manner using the suction head and the like described above, the blanks stacked in layers in the hopper are intimately in contact with one another. If an attempt is made to attract and deliver only one of the blanks, therefore, the next blank overlying it may be simultaneously delivered, in some cases. As a measure to counter this double-sheet blank delivery, there may be a proposal, for example, to secure a gap in advance between a blank to be delivered and the next blank in the hopper so that the blank to be delivered and the next blank can be separated from each other by utilizing the gap.
If the gap is previously secured between the blank to be delivered and the next blank, however, the blank to be delivered is quickly separated from the next blank to be detained in the hopper, so that the pressure of air in the gap then sharply lowers, thereby producing suction force between the two blanks. As the blank is delivered, therefore, the next blank is urged to slip out of the hopper outlet, accompanying the blank being delivered. If the suction force exceeds the force of the next blank to be detained in the hopper by means of its elastic force, as this is done, double-sheet blank delivery may occur. In consequence, a defective package may be produced or the operation of the whole system including a blank feeding path and the packaging machine may be interrupted, thus resulting in lowering of the production efficiency of the packaging machine.
An object of the present invention is to provide a feeding apparatus capable of securely delivering material sheets stacked in layers in a hopper one after another.
In a feeding apparatus of the present invention, material sheets are stored in a hopper in a manner such that they are vertically stacked in layers, the hopper having a hopper outlet opening upward or downward, and are restrained from escaping by means of rows of stoppers at the hopper outlet. Further, the feeding apparatus comprises a sucking member capable of getting into and out of the hopper through the hopper outlet. The sucking member can attract and deliver that material sheet which faces the hopper outlet as it gets into and out of the hopper.
In the feeding apparatus of the present invention, the stopper rows are technical means that contributes most to the solution of the aforementioned problems. Each stopper row includes a plurality of stoppers that are arranged at intervals in the longitudinal direction of the material sheets. Each stopper has a guide surface and a restrainer lug. More specifically, the guide surfaces are inclined gradually to reduce the allowable passage width for the material sheets in the direction of delivery by the sucking member, and can guide the side edges of the material sheets as the material sheets are delivered. On the other hand, the restrainer lugs extend from the respective terminal ends of the guide surfaces to the inside of the hopper outlet, and allow only the material sheet attracted to the sucking member to be elastically deformed to get over the restrainer lugs.
If the material sheets are stored in a stack in the hopper that has a downward hopper outlet (for the so-called bottom delivery), for example, the side edges of the lowest sheet and several material sheets that overlie the lowest sheet are supported on the aforesaid guide surfaces. Since the inclination of the guide surfaces gradually reduce the allowable passage width for the material sheets in the direction of delivery or downward, each of the material sheets is contracted in the width direction and elastically deformed into a downwardly convex shape as it descends, while it can be detained in the hopper by means of its restoring force. The lowest material sheet is deformed to the maximum degree, and a gap is formed between the lowest material sheet and the directly overlying material sheet owing to the difference in warps between the material sheets in the direction of delivery.
As the lowest material sheet is delivered by the sucking member, it is further contracted in the width direction with its opposite side edges guided on the guide surfaces, so that the aforesaid gap enlarges further. As this is done, the stopper rows never close the gap, and air introduction passages are formed for the enlarging gap between the individual stoppers. Thus, air can be introduced into the enlarging gap through the spaces between the stoppers during the material delivery, so that the pressure of air in the gap can never lower.
Thereafter, the opposite edge portions of the attracted material sheet are caught by the restrainer lugs. The delivery operation of the sucking member causes the material sheet to be elastically deformed to a higher degree, resisting the catch by means of the restrainer lugs. When the side edges of the material sheet get over the restrainer lugs, the delivery of the lowest material sheet is completed. On the other hand, the material sheets that overlie the lowest one cannot be elastically deformed against the catch by means of the restrainer lugs, and are detained in the hopper with aid of its restoring force, so that securer single-sheet delivery can be achieved.
Preferably, the aforesaid stopper rows are arranged in pairs on the opposite sides of the hopper outlet, respectively so that the opposite side edges of the material sheet can be kept symmetrical as the sheet is regulated and guided. In this case, moreover, the restrainer lugs are arranged symmetrically, so that they can catch the material sheet more securely.
Preferably, the sum total of the respective widths of the guide surfaces contacting the material sheet in each stopper row is adjusted to half or less of the longitudinal dimension of the sheet. In this case, air introduction passages having a width of at least 50% or more in view of the sheet length at one side edge of the material sheet can be secured at the time of delivery.
Preferably, the inclination of the guide surfaces has a gradient of 45xc2x0 or less to the direction of delivery of the material sheet, in particular. If the inclination of the guide surfaces is within this range, an appropriate gap can be secured between that material sheet which faces the hopper outlet and the next material sheet.
Further, the restrainer lugs extend at a separating angle of 0xc2x0 to 45xc2x0 from a plane in contact with the hopper outlet. If the length of extension of the restrainer lugs is fixed, the catch of the material sheet is the strongest with the separating angle of 0xc2x0. If the angle exceeds 45xc2x0 the catch becomes extremely weak. Preferably, therefore, the separating angle of the restrainer lugs should be restricted to the range from 0xc2x0 to 45xc2x0.
Furthermore, the feeding apparatus of the present invention comprises support members. The support members restrain escaping of the material sheets in the hopper at the side edges of the material sheets. The support members are formed having rows of stoppers. The stopper rows support the side edges of the material sheets stacked in the hopper and secure a gap between the material sheet facing the hopper outlet and the material sheet overlying the same. Introduction passages through which the outside air is introduced into the gap during the delivery by the sucking member are formed between the individual stoppers of the stopper rows. Restrainer members are formed individually on the stoppers. When the material sheet is caused to slip out of the hopper outlet and then delivered by the sucking member, the restrainer members can restrain escaping of the next material sheet overlying on the material sheet.